Contemporary Floodplain Forest Evolution along the Middle Ubaye River, Southern Alps, France

Piégay, Hervé; Salvador, Pierre‐Gil

doi:10.2307/2997340

Cited by 37 publications

(23 citation statements)

References 15 publications

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“…Moreover, the high rates of channel narrowing, to typically around 50 per cent of the former active channel width, seem too large to be explained by the relatively subtle hydrologic differences in the basins displaying a change. Hence, the magnitude of flood discharge variability is considered to explain only short-term fluctuations of the contact between active channel and riparian forests, as observed along the Ubaye River (Piégay and Salvador, 1997). The trend of channel narrowing after 1950 is more persistent and extensive.…”

Section: -1970: Channel Narrowing Associated With Floodplain Landmentioning

confidence: 99%

“…On the Ubaye River, Piégay and Salvador (1997) previously showed from dendrochronological evidence that vegetation encroachment began abruptly around 1920. This major change has been strongly associated with torrent regulation realized from 1880 to 1900 15 km upstream.…”

Section: -1950: Channel Narrowing Associated With Changes In Bedlmentioning

confidence: 99%

“…The mining-induced incision occurred after the vegetation encroachment in active channels, and cannot be viewed as a cause of channel narrowing. In the Ubaye and Giffre Rivers, which had already narrowed by 1950, between 1 and 3 m of channel degradation occurred in the 1970s, without any channel narrowing (Piégay and Peiry, 1997;Piégay and Salvador, 1997). These examples suggest that the disconnection of alluvial surfaces by degradation is not necessarily an important factor enhancing the development of vegetation on valley floors when the active channel has wide unvegetated gravel bars, because degradation due to mining affects not a small part of the active channel, but the whole width, comprising annually relocated low-flow channels and gravel bars.…”

Section: -1970: Channel Narrowing Associated With Floodplain Landmentioning

confidence: 99%

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Causes of 20th century channel narrowing in mountain and piedmont rivers of southeastern France

Liébault

Piégay

2002

Earth Surf Processes Landf

338

190

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Extensive channel narrowing in southeastern France provides an illustration of geomorphic response to land-use changes. The study region comprises a range of environments, from large piedmont and intramountain gravel-bed rivers, to small mountain streams. Field measurements and analysis of historical data demonstrate two distinct periods of channel change. From 1850 to 1950, channel narrowing is interpreted to be the result of a recovery process in response to widespread channel destabilization induced by major floods during the second half of the 19th century. At the time, the largely deforested basins were highly responsive to flooding, whereas the recovery process was accelerated by floodplain and basin-scale land use changes (afforestation) and torrential control works, which in turn reduced sediment delivery and enabled vegetation development in channels. From 1950 to 1970, channel narrowing accelerated in most of the studied rivers. This recent phenomenon is considered as a human-induced fluvial adjustment, directly related to forest development on river margins and human abandonment of intensive floodplain land uses. At the same time, long-profile degradation occurred as a result of long-term bedload supply decrease. In small mountain streams, channel narrowing is mainly explained by channel incision which seems to progress from upstream where sediment sources are progressively stabilized by afforestation.

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Section: -1970: Channel Narrowing Associated With Floodplain Landmentioning

confidence: 99%

Section: -1950: Channel Narrowing Associated With Changes In Bedlmentioning

confidence: 99%

Section: -1970: Channel Narrowing Associated With Floodplain Landmentioning

confidence: 99%

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Causes of 20th century channel narrowing in mountain and piedmont rivers of southeastern France

Liébault

Piégay

2002

Earth Surf Processes Landf

338

190

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“…• evolution of stream beds, gravel banks and islands as a consequence of sedimentary balance and heritage of mountain erosion (Piégay and Salvador, 1997;Piégay et al, 1999;Vautier, 2000;Liébault and Piégay, 2001);…”

Section: Introductionmentioning

confidence: 99%

Processes, spatio‐temporal factors and measurements of current erosion in the French Southern Alps: a review

Descroix¹,

Mathys²

2003

Earth Surf Processes Landf

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Present erosion in mountainous areas of Western Europe causes land management problems, particularly for areas located downstream of erosion zones. Except for transalpine roads and ski resorts, economic activities no longer require as much space as they did in the past. Therefore, natural reforestation has provided significant protection for alpine hillslopes during the 20th century. However, extreme floods continue to cause severe damage in intra-alpine valleys, as well as in piedmont and surrounding plains, making the study of present water erosion phenomena very important.Many studies have investigated the processes and factors of water erosion on slopes at both the catchment and plot scales. They have focused on rock fragmentation and transportation in different fields, the spatial and temporal explanatory variables, the consequences downstream (flooding, sedimentation, river bed evolution) and the impact of floods.In the French Alps, present erosion has been studied in a variety of outcrops, with several recent studies conducted in fields such as marls, clayey deposits, molasses and moraines. These kinds of outcrops are found throughout the alpine massif, including an area of special interest on the great Jurassic black marl outcrop where badlands are frequently observable. Geomorphologists and hydrologists have been particularly interested in the strong erosion processes in marls, seeking to determine the main patterns and the impact of spatial and temporal factors on soil loss quantities.The main climatic factors of rock disaggregation were found to be the freeze-thaw and wet-dry cycles, which destroy rock cohesion, and the splash effect of rain. The principal site variables are vegetation cover, exposure and dip-slope angle. Erosion rates are two or three orders of magnitude higher on bare soils than on pastures; northern aspect slopes suffer two to four times as much soil loss as southern aspect slopes. Finally, the angle formed by the slope and the dip also determines different behaviours: erosion rates are higher when slope and dip are perpendicular than when they are parallel. The transportation agents are mostly debris flows and runoff caused by intense precipitation. Annual erosion depth in the marls is generally assumed to be substantial, up to 10 mm. The high value can be explained by the severity of the climatic conditions and the brittleness of the lithology, which results in numerous fractures.

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“…This finding is also valid for many other floodplain landscapes in Europe (Large & Petts, 1996, Konold, 2005. However, a study of rural mountainous floodplain landscapes in France revealed the contrary finding that floodplain forests -following deforestation in previous centuries -have again expanded since 1920 due to watershed reforestations and the abandonment of pastoral activities (Piégay & Salvador, 1997).…”

Section: /298mentioning

confidence: 80%

Rivers, regulation and restoration: land use history of floodplains in a peri-urban landscape in Luxembourg, 1777 - 2000

Schaich¹,

Karier²,

Konold³

2011

European Countryside

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This paper discusses the historical changes to and the uses of floodplain landscapes in Luxembourg from 1770-2000 as a case study of a region with a rural past and a peri-urban present. Based on the historical landscape analysis approach, the study comprises historical evidence of written, cartographic and oral sources collected at a regional (Gutland) and a local (Syr Valley) level. The floodplains investigated were old cultural landscapes, shaped by agriculture, livestock husbandry, river regulation measures, land improvement, milling, navigation, mining and fisheries. Landscape change has been characterised by different periods of intensity, however it was not until the last century that these changes had a large-scale impact, inducing a complete loss of several ecological and socio-economic functions. A historical perspective of local landscape conditions and land use change is needed to maintain landscape identity in a contemporary peri-urban environment, and to base planning and restoration activities on reliable data.

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Contemporary Floodplain Forest Evolution along the Middle Ubaye River, Southern Alps, France

Cited by 37 publications

References 15 publications

Causes of 20th century channel narrowing in mountain and piedmont rivers of southeastern France

Causes of 20th century channel narrowing in mountain and piedmont rivers of southeastern France

Processes, spatio‐temporal factors and measurements of current erosion in the French Southern Alps: a review

Rivers, regulation and restoration: land use history of floodplains in a peri-urban landscape in Luxembourg, 1777 - 2000

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